Compensated befbigebatof



May 15, 1945- 'l B. E. sHAw ETAL 2,376,092

COMPENSATED RERIGERATOR THERMOSTAT Filed July 14, 1942 Patented May 15,y `1945 UNITE-o `STATES PATENT ortica COMPENSATED REFBIGERAUI' THERMOSTAT Burton E. shaw, Bristol, and Earnest F. Swanson,

Goshen, Ind., assignors to Penn Electric Switch Co., Goshen, Ind., a corporation of Iowa Application July 14, 1942, serial No. 450,862

s claims. (c1. zoo-fissi o Our present invention. relates to a refrigerator thermostat which is compensated against widen- Aing of the differential thereof due to heat generated by the passage of current through the elements .ofi the thermostat, and which may 'be further compensated to secure va cold anticipa tion feature. One object of the invention is to provide a thermostat .for refrigerators or other cooling equipment which is compensated by a simple thermal responsive means associated with an ordinary thermostat.

A further object is to provide a means to reduce the diiferential of operation of a thermostat for cooling equipment where such thermostat is orl1y. The compartments I4 and jlb-are insulated with respect to each other by the base IIJ.

` 1n thejcasing I3, such mechanism-bein of the general type shown in shaw Patent No.v 265,495,

dated December 9, 1941, and comprises'lbriefly v the following elements: A bracket comprising ay plate I6 and two` upstanding sides II is secured to the base Illas by a pair of screws I8. The sides I1 carry a pivot pin I 8, for a coiled bimetallic velement: I9, which isI shown as formed in four l. separate coils, side by side, to secure suflicient widened as to diierential, due to the now ofcurrent through the elements of the control the main thermal responsive element of the thermostat and the compensating element.

With these and other objects in view, our invention consists in the construction, arrangement and combination of the various parts of our device whereby the objects' .contemplated are attained, as hereinafter more fully set forth, pointed out in our claims and illustrated in the accompaning drawing, in which:

Figure 1 is a front view of a thermostat embodying our invention, the casing thereof being shown in section;

Figure 2 is a side elevation ofF-igure 1 with a portion of the casing broken away;

Figure 3 is a sectional view on the line 3--3 of Figure 1, showing details 'of construction; and

.Figure 4 is a partial rear view of our thermostat, showing thecompensating means therein.

On the accompanying drawing we have used the numeral I0 to indicate generally a base, which is preferably made of insulating material. A casing I2, which-may be made of metal, serves as a sub-base for the base III, and a casing member 'I3 serves as an enclosure casing for switch mechanism on the front of the base III. The casings I0 and I2 divide the thermostatic'structure into two power to operate relatively heavy contacts and thereby -directly control electric motors, such as .the type used forrefrigerant compressors or. other cooling equipment. The bimetal element I9 has 1 its inner end secured to a. cross-'bar -120 of a U- shaped bracket, which has an adjusting screw 2I threaded into it. The adjusting screw 2| extends through an arcuate slot 22 of another U-shaped bracket 23, wherebythe brackets and 23 may be adjusted with relation to each other. This is a factory adjustment.

The outer end of the bimetal coil I3 is secured to a block of insulation 24 having an armature,

arm 25 mounted thereon. The arm 25 is adapted to Acooperate with a horse-shoe magnet 26 to secure snap action in the usual manner. The magnet 28 is supported on a bracket 21 which, in turn. is secured, as by screws 2, tothe base n .l

:Ehe-arm, 25 carries a leaf spring 29 provided with a movable contact 30. The contact 30 is adapted to, at times, engage a stationary contact 3l which is adlustable'relative to the bracket'21 by being screw-'threaded therein. An adjusting knob 32 is provided for adjusting the range of operation of the switch structure by rotating the `screw-carried contact 3I, and is provided with an indicating nger 33 movable in an arcuate slot 34 oi the bracket 21.

Our compensating mechanism includes a bimetallic strip 35 secured to a `Ushaped bracket 36 which, in turn, is pivoted on a pin 31. The pin 31 is carried in a pair of bosses 33, formed/ in the lback of the base, and a plate voi' insulation 39 is secured to these bosses by screws I0. 'I'he screws 40 also secure a terminal vblock 4I to the Ibosses 38, with the plate 39 interposed between the terminalI block and the bosses.

The upper end of the bimet-allic strip 35 is provided with a notch receiving a pair of iiattened compartments, indicated at `I4 and I 3, respective- 55 slots 42 of an adjusting nut 43. The adjusting nut 43 is threaded on a screw u having a iiange 45 held against the back oi' the base I0 by aspring The usual thermostatic mechanism is provided dii. The spring drs is interposed between an ad justine,T dial dl and a head Il@ on the screw ll. The dial dl has periphery lrnurled and projected through a slot #lil at the top of the casing lll to a position where it may be readily engaged by the linger of an operator and rotated. The means of connection between the adjusting dial lll and the screw M is a cross-pin 5d and slots 5l.

The dial il is limited to slightly less than one rotation by a slot di therein anda projection till from the base lll. The dial, however, may be recalibrated relative to the screw t4 by pulling it outwardly against the bias of the spring lli after the casing i3 is removed and after a holding screw tid and a washer to have been removed. This will disassoclate the cross-pin E@ from one oi its slots lil, whereupon the dial may be rotated a quarter turn, either right-hand or lefthand, as required, and the cross-pin reentered in one of the slots.

The lower end of the bimetellic strip Sill is operatively connected with the bimetal coil l@ to adjust it for compensating purposes by means ci' a thrust pin rlire thrust pin td has reduced ends El' and lill passing through perforations ofthe birnetallic strip ld and the bracket respectively. The pin 5d extends loosely through an opening dt in the base it. The bracket 2li and the strip 35 are retained in eneasement with the shoulders of the pin til by a spring tu connected between the cross-piece til and an ear tl i'orrned on the bracket iti.

The terminal bloclr di has terminal screws lli and t3 mounted therein. Terminal lugs lill and dit have the screws di! and dthreaded therein and the terminal lues are connected respectively to a lead lili and a. heater wire lil. The lead tt connects by a screw lid to the bracket El so that the current flows through the brochet to the stationary contact di. The heater lll is con nested to a screw td threaded in a braciret'lti which, in turn, is connected by a rivet 'll with a lue: l2. The lug 'll is connected by a flexible pig-tail connection "i3 to a lug M of the armature arm lid, whereby current is carried ironi the m0vable contact til. The terminals tt and lill may then be connected in series with a refrigerantv compressor motor .or other device, electrically operable to effect the operation of cooling eduipment.'

Uur thermostat may be connected to a wall oi a room or or a refrigerated space, by a pair of mounting screws l5 extending through the base .lli and through the plate 39 and the terminal bloei; lll into the surface of thefwall.

Practical operation l'n the operation oi' our compensated re'frieeraf tor thermostat, the thermostatlcally controlled blmetal coil i9 operates in the-usual manner, uncoiling when temperature lowers-and thereby tending to open the s'virltchffrom the position of Figure 3 to the position of Figure 2. When temperature rises, the coil tends to contract for closing the circuit, thereby operating the refrigerating mechanism or the cooling mechanism controlled thereby, and, thereupon, reduce the The I .y ambient temperature finds' its way to the bimetal ltemperature ambient to the thermostat.

Y carrying elements within the compartment i4 toy narcose To compensate for the undesirable widening of the differential we have provided the birnetallic strip in a compartment td, insulated :from the compartment l5 so that it is not subjected to ambient air temperature, and we further provide the heater lll for the purpose of raisinsy the temperature in the compartment ill surrounding the bimetallic strip a predetermined degree so that the birnetal element will warp whenever curu rent flows through the control structure. The direction of warpage is left hand at the lower end of the birnetal strip so as to permit the pin to be moved toward the left by the spring til, thereby tending to open the contacts lill and lll. The result/is a narrowing of the differential so as to compensate for the tendency for it to be widenedfby heat generated in the compartment lll by current how through the elements ci the control mechanism therein.

We prefer to more'than compensate for the widening or? the differential in the compartment it so as to secure a cold anticipation feature by anticipating a drop in temperature alter the con trol switch is closed, and thereby allowing the switch to open at a temperature aiew degrees higher than it otherwisev would if the teniperature ambient to the coil it were the only consideration. Thus, by providing the bimetal element td responding to current now and not to ambient temperature, and mechanically connecting it with the temperature responsive means in the com pertinent id so that it operates it in the proper direction when current -rlows through the coinpartment lll, we are able to compensate lor -v/ideued" differential, and go further in order to reduce the differential to practically zero, or even provide a negative differential il desired. Any degree ci compensation or over-compensation can he secured by the proper size or the wire bl with respect to the current flow through the control switch, as determined by the size ol the motor or 'other electric equipment beine controlled. In some installations it may not even be necessary to provide 4the heater lll, if there is sufficient resistance to current flow in the circuit generate the required heat.

Dur compensation mechanism .lor a refrigerator thermostat is particularly adaptable for switches V:l'or directly controlled refrigerant compressor motors, whereas, heretofore, relays have been used, due to the heavy ow of current throughthe control switch ifa relay is not used, Widening theA dierential to en undesirable degree. With our arrangement a, motor controlling thermostat isv possible without an undesirably wide differential of operation of the switch mechanism, and any degree o1' reduction of the differential desired may be secured.

Some changes may be lmade in the construction and arrangement of the parts of our device without departing from the real spirit and purpose of our invention, and it is our intention to cover by our claims any modiiled forms of structure, or use of mechanical equivalents, which may be reasonably included within their scope.

We claim as our invention: l

n l. A refrigerator thermostat comprising a base of insulating material, a casing on one side thereof having temperature responsive control-means therein and having openings for the passage of air therethrough; a second and closed casing on the other side of said base having temperature responsive compensating means therein, said temperature responsive control means being subjected t ambient temperature owing through its casing and to heat generated by the passage of current through said temperature responsive control means, said temperature responsive compens-ating means being responsive only to heat generated by the flow of current through said thermostat, and a thrust pin of vinsulating material extending through said base for mechanically and non-thermally connecting said temperature responsive compensating means with saidtemperature responsive control means to readjust the control means and thereby lower its differential of operation in response to heat generated by the flow of current through said thermostat.

2. In a compensated thermostat for cooling mechanism, a base, a casing on each side of said base, said base thermally separating said casings from each other, thermostatic control mechanism in one of said casings, saidcasing having openings therein, said thermostatic control mechanism being responsive to the temperature of air anism against remaining for a. prolonged period of time in position calling for lowering of the temperature of such air comprising thermal responsive means in said other casing, said other casing being closed, said thermal responsive means being subjected to heat produced in said closed casing by current ow through said thermostat, and a thrust pin extending through said base for transmitting movement from said thermal responsivemeans to said thermostatic control mechanism for modifying the action 0i the ing material, a pair of casings on opposite sides thereof thermally insulated from each other by said base, a temperature responsive control means in one of said casings, a, temperature responsive compensating means in the other one, the interior of said first casing being subjected to ambient temperature and to heat generated by passage of current through the temperature responsive control means therein, said second casing being closed and thereby responsive only to heat generated 'by the flow or current therethrough, and a heat insulating thrust connection through said base from said temperature responsive compensating means to said temperature responsive control .means to change the adjustment of the latter in' a direction tending to open the circuit controlled thereby due to a rise intemperature in said second casing.

BURTO E. SHAW. manner F. swANsom 

